The present invention relates to a circuit of eliminating motional vector remaining caused by transmission error in compensating the motional vector of MUSE type television receiver.
The prior art for subsample interpolation equipment of compensating the motional vector is shown in FIG. 1.
In FIG. 1, the reference number 1 shows video signal input terminal inputting the video signal transmitted at the standard rate of 16.2 MHz, the inputted video signal is switched at the standard rate of 32.4 MHz together with the output signal from the motion compensation field memory 4 which performs the motion compensation according to the motion vector from the motion vector input 5, and then is stored at the non-motion compensation field memory 3 which stores one frame signal at the standard rate of 16.2 MHz.
The motion vector input 5 inputs an interframe motional vector transmitted from the sending side, and the subtracter 6 computes a new interfield motional vector from the difference between the interframe motional vector inputted from the input 5 and the interframe motional vector delayed as much as one field by the interfield delay device 7.
The motion compensation field memory 8 stores one frame signal at the standard rate of 16.2 MHz from the switch 2, performs the motion compensation according to the one interfield motional vector from the subtracter 6, and its output is converted from 32.4 MHz to 24.3 MHz by the frequency converter 9, and then is interpolated between fields by the interfield interpolation filter 11 together with the output of the frequency converter 10 which converts the frequency transmitted from the switch 2.
The sample of the present field transmitted from the switch 2 is converted by the frequency converter 12, and is interpolated within field by the intra-field interpolation filter 13.
The mixer 14 mixes the outputs from the interfield interpolation filter 11 and the intra-field interpolation filter 13 according to the detected motion quantity 16, and outputs the mixed signal to the video signal output terminal 15.
As shown above, the motion vector input 5, the subtracter 6, and the interfield delay device perform the function computing motion compensation quantity of one interfield from an interframe motional vector, and an example of the operation is shown in FIG. 2.
FIG. 2 shows the motional vector diagram in case of turning again to the still picture after the panning is produced from the still picture.
In FIG. 2, X axis shows the horizontal axis of the picture and Y axis shows the vertical axis thereof.
Each field of the video signal is shown as the points c0, d0, a1, c1, d1, a2, b1, etc.
The interfield motional vector is shown as the vectors A1, B1, C1, etc., and the computed one interfield motion compensation vector is shown as the vectors a1, a2, c1, d1, etc.
For example, the vector A1 is the motional vector compensating a1 field as based on c1 field and the vector B1 is the motional vector compensating a1 field as based on b1 field. Between the vectors C1, A1, D1 . . . and the vectors c1, a1, d1, . . . , the following equations are formed. EQU A1=a1+b1,B1=b1+c1 , . . . , EQU or EQU a1+A1-b1, b1+B1-c1 , . . .
In FIG. 2, c0-a1 field shows the still picture, b1-c2 field shows the panning, and d2-a4 field shows the still picture. Therefore, if the panning is produced in the still picture, EQU C0=0,D0=a1, A1=a1+b1 , . . . EQU a1=D0,b1=A1-b1 , . . .
In case of turning to the still picture after the panning, EQU . . . ,A2=a2+b2,B2=b2+c2,C2=c2,D2=0, . . . EQU . . . ,a2=A2-b2,b2=B2-c2,c2=C2,d2=0, . . .
By the said computation, one interfield motional vector is obtained from an interframe motional vector being transmitted.
This prior art can obtain an interfield motional vector from an interframe motional vector, but it had a problem remaining the transmitting error due to the feedback loop for computing the interfield motional vector.
To express that relation by a numerical formula, the interframe motional vector transmitted at the nth field is defined as M[n], and the interfield motional vector computed by an operation is defined as m[n].
According to this definition, EQU m[n+1]=M[n]-m[n] (1).
If the interfield motional vector including an error (e[n]) at the nth field is defined as m [n], EQU m[n+1]=m[n]+e[n] (2).
The interfield motional vector at the [n+1]th filed, EQU m[n+1]=M[N]-m[n] (3).
Here, if the formula (3) is replaced by the formula (2), EQU m[n+1]=M[n]-{m[n]+e[n]} EQU m[n+1]e[n+1]=M[n]-{m[n]+e[n]}.
The error component included at the interfield motional vector of the [n+1]th field, EQU e[n+1]=-e[n].
If this is again expressed by the error (e[0]) included at m[0] as the transmitting error produced in transmitting the first state M[1], ##EQU1##
Accordingly, the first error e[0] is not reduced, and is remained.
FIG. 3 is a diagram of showing an influence of the motional vector transmission error. In FIG. 3, an error vector e shows that an error adds in transmission of the motional vector A1. And also a solid line shows the interframe being transmitted, a broken line shows the interfield motional vector obtained by operation, and a dashed line shows the motional vector in case that an error doesn't exist. As shown in FIG. 3, the transmission error vector e has continuously an influence on correction of the interfield motional vector, also has an influence on the still picture by continuous vibration (+e,-e) after d2 field of the ending of panning, and then finally it causes degradation on picture quality. Besides, in case that continuous errors are produced on the motional vectors being transmitted, the errors are remaining, are summed up, and it causes worse degradation.